Re: [PATCH] coresight: etm4x: fix mis-usage of nr_resource in sysfs interface

[Mathieu Poirier <mathieu.poirier@linaro.org>]

On Fri, Sep 04, 2020 at 06:08:46PM +0800, Zhouwen (Jonathan, Turing) wrote:
> 
> Hi Mathieu,
> 
> Thanks for your review.
> 
> 在 2020/9/4 1:22, Mathieu Poirier 写道:
> > On Wed, Sep 02, 2020 at 03:52:56PM +0800, Jonathan Zhou wrote:
> > > The member @nr_resource represents how many resource selector pairs,
> > > and the pair 0 is always implemented and reserved.
> > > So let's multiply by 2 when displaying the implemented resource seletors
> > > and resetting the seletor configuration .
> > > And also update the validation of the input @idx.
> > > 
> > > Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
> > > Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
> > > Cc: Mike Leach <mike.leach@linaro.org>
> > > Cc: Shaokun Zhang <zhangshaokun@hisilicon.com>
> > > Cc: lizixian@hisilicon.com
> > > Signed-off-by: Jonathan Zhou <jonathan.zhouwen@huawei.com>
> > > ---
> > >   drivers/hwtracing/coresight/coresight-etm4x-sysfs.c | 15 ++++++++++-----
> > >   1 file changed, 10 insertions(+), 5 deletions(-)
> > > 
> > > diff --git a/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c b/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c
> > > index b673e738bc9a..635b93d20efa 100644
> > > --- a/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c
> > > +++ b/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c
> > > @@ -143,8 +143,10 @@ static ssize_t nr_resource_show(struct device *dev,
> > >   {
> > >   	unsigned long val;
> > >   	struct etmv4_drvdata *drvdata = dev_get_drvdata(dev->parent);
> > > -
> > > -	val = drvdata->nr_resource;
> > > +	/* @nr_resource represents how many resource selector pairs,
> > > +	 * hence multiply by 2.
> > 
> > Your comment said it correctly, @nr_resource present the number of _pairs_.  As
> > such the code is correct and there is no need to multiply by 2.
> > 
> 
> Sorry for not mentioned the reason of modified this. From the function
> @res_ctrl_store, we can see that only one individual resource selector can
> be accessed via the ->res_idx. Therefore, it may be better to show the
> number of individual resource selectors.

The end result does not change, i.e this entry represent the number of pairs
available on the system.

> 
> > > +	 */
> > > +	val = 2 * drvdata->nr_resource;
> > >   	return scnprintf(buf, PAGE_SIZE, "%#lx\n", val);
> > >   }
> > >   static DEVICE_ATTR_RO(nr_resource);
> > > @@ -236,7 +238,7 @@ static ssize_t reset_store(struct device *dev,
> > >   	}
> > >   	config->res_idx = 0x0;
> > > -	for (i = 0; i < drvdata->nr_resource; i++)
> > > +	for (i = 2; i < 2 * drvdata->nr_resource; i++)
> > >   		config->res_ctrl[i] = 0x0;
> > 
> > This hunk is correct - please send a patch for it.
> 
> Ok.
> 
> > 
> > >   	config->ss_idx = 0x0;
> > > @@ -1663,8 +1665,11 @@ static ssize_t res_idx_store(struct device *dev,
> > >   	if (kstrtoul(buf, 16, &val))
> > >   		return -EINVAL;
> > > -	/* Resource selector pair 0 is always implemented and reserved */
> > > -	if ((val == 0) || (val >= drvdata->nr_resource))
> > > +	/*
> > > +	 * Resource selector pair 0 is always implemented and reserved,
> > > +	 * namely an idx with 0 and 1 is illegal.
> > > +	 */
> > > +	if ((val == 0) || (val == 1) || (val >= 2 * drvdata->nr_resource))
> > >   		return -EINVAL;
> > 
> > The index, i.e ->res_idx, represent pairs an not individual resource.
> >
> > Thanks,
> > Mathieu
> > 
> 
> If we want all of the ->res_ctrl accessable, the ->res_idx should represent
> individual resource. That's the reason.

I see your point now.  I think the above condition should be simplified:

        if ((val < 2) || (val >= 2 * drvdata->nr_resource))

> 
> Best regards.
> 
> Jonathan.
> 
> > >   	/*
> > > -- 
> > > 1.9.1
> > > 
> > .
> > 

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